The present invention relates generally to a device and method for preparing a tissue specimen for frozen sectioning in surgical pathology, histopathology and MOHS. More particularly, the present invention relates to a device and method for preparing tissue sections for microscopic examination during surgery using frozen section technique for extirpation of neoplasms.
Frozen sectioning is used in surgical pathology, histopathology and MOHS to relatively quickly yield tissue sections for microscopic examination. Frozen sectioning is particularly useful for tumor margin analysis. The use of histologic sections guides or assists a surgeon during surgery to determine whether all of the cancerous cells or neoplasm are excised and, if not, where to make further surgical excisions. The technique involves an iterative process of excising tissue, examining it and then excising additional tissue as dictated by the examined tissue sample. More specifically, a portion of tissue is excised and sliced into sections in a microtome. The tissue slices are examined microscopically and then another area is selected for excision based on the examination of the slices. The next tissue sample is excised and the sample is sliced into sections which are examined microscopically to determine whether they contains residual neoplasm. Mapping techniques are used to record tumor location and to determine which tissue adjacent to the previous tissue sample should be excised next. The procedure is repeated until the excised tissue specimen shows no residual neoplasm.
In general, the preparation of tissue slices involves encasing or embedding the tissue specimen in an O.C.T. substance and then slicing the solidified block in a microtome, yielding slices that contain a generally peripheral portion of O.C.T., with an internal portion of tissue section in most of the slices. xe2x80x9cO.C.T.xe2x80x9d stands for xe2x80x9coptimal cutting temperaturexe2x80x9d and, as the name suggests, is a substance that makes it easier to cut or slice the tissue specimen. O.C.T. is typically liquid or semi-liquid at room temperature. It is poured in liquid form over the tissue specimen and then is solidified by cooling it to a temperature below its freezing point.
Typically, an excised tissue portion is generally curved or parabolic in cross-section. However, to obtain tissue slices or sections that are satisfactory for microscopic examination, the face of a specimen to be sectioned should be planar and parallel to the path of relative movement between the microtome knife and the specimen, thus ensuring that all of the surgical margin is included in the first several slices or sections. When performing frozen sections for tumor extirpation, this is of particular importance for accurate histologic or microscopic interpretation. For general diagnostic frozen sectioning, this is advantageous because it saves time. Therefore, the parabolic or curved specimens should be flattened before they are encased in O.C.T. to produce good quality slices. This is often difficult and tedious because the edges of tissue specimens are typically inclined to curl or not lie flat.
The frozen section technique requires the fast preparation and examination of fresh tissue. Therefore, techniques used to prepare fixed tissue for permanent section analysis are not applicable.
One method of preparing fresh tissue samples for slides for use in a frozen section technique is described in U.S. Pat. No. 4,695,339 to Rada. Rada describes placing a tissue specimen on a polished platform, placing a membrane over the specimen, manipulating the specimen with a tool to flatten it on the platform, then using a vacuum device to further flatten the specimen against the platform. Rada then describes freezing the tissue specimen by applying liquid nitrogen to it with a swab. Thereafter, the frozen specimen is entombed in O.C.T. by applying the O.C.T. to the platform that holds the tissue and to another mateable platform. The two platforms are pressed together until the O.C.T. solidifies. The platforms are then pulled apart, and the solidified block of O.C.T with the tissue specimen embedded therein is removed from the platform to which it adheres. This process involves one step for freezing the tissue and then later in the process requires another step for solidifying the O.C.T. Further, the process requires the use of vacuum equipment.
The efficiency and accuracy of the frozen section technique is affected by the quality of the tissue slices. What has been needed is an elegant and effective method and device for preparing tissue slices or sections that allows the entire excised tissue surface to be examined. Further, a method and device are needed which minimize the size, bulk, and power requirements of the equipment involved in the process. Still further, what is needed is a process that reduces the amount of time required for preparing tissue sections.
The present invention provides a device, method, and kit for preparing tissue samples for sectioning. According to one aspect of the invention, a device is disclosed that includes a cup-shaped receptacle having a planar surface on which a specimen is flattened. The cup shape of the receptacle allows OCT to be poured directly into the cup over the specimen. The receptacle accommodates a chuck member that has a planar surface sized to be received in the cup-shaped receptacle.
According to another aspect of the invention, a method is disclosed for preparing tissue samples for sectioning. The method includes the steps of placing a tissue sample or specimen on a planar surface inside a cup-shaped receptacle, then pouring or applying O.C.T. into the receptacle in an amount sufficient to cover the specimen. Next, a chuck member, having a planar surface sized to be received within the cup-shaped receptacle, is inserted into the receptacle. The O.C.T. forms a barrier between the chuck planar surface and the specimen so that the specimen does not adhere to the chuck. The assembly of the receptacle and chuck with the O.C.T. and specimen therebetween is exposed to a temperature low enough to quickly freeze the specimen and the O.C.T., creating a solidified block of O.C.T. with the specimen embedded therein. The solidified block is then sliced for examination.
According to another aspect of the present invention, a method is disclosed for preparing a tissue specimen for sectioning, including the steps of: providing a cup-shaped receptacle having a first generally planar surface; providing a chuck member having a second generally planar surface sized to be received within said receptacle; placing a tissue sample on said receptacle planar surface; pouring a substance in liquid form into said receptacle; inserting said second planar surface into said receptacle; decreasing the temperature of said substance at least to its freezing point such that said that substance forms a solidified block with the specimen frozen therein.
According to another aspect of the invention, a method is disclosed for conveniently forming a solidified block of O.C.T. with tissue embedded therein on a chuck. The chuck, loaded with solidified O.C.T. and tissue, is then easily carried to a microtome for slicing while preserving the orientation of the flattened tissue surface.
According to another aspect of the invention, a device is disclosed for facilitating the alignment of a chuck member in a cup-shaped receptacle which thereby assists in orienting the chuck to the tissue specimen. In disclosed embodiments, the alignment device is configured with a handle that is spaced from the assembly of the chuck member and the receptacle. The handle allows the user to dip the entire assembly of the chuck member and the receptacle into liquid nitrogen for simultaneously freezing the specimen and encasing it in a solidified block of O.C.T.
According to another aspect of the invention, an assembly having a based for receiving a receptacle and a cap for orienting the chuck within the receptacle and for holding the chuck in proper orientation during dipping of the cup and chuck into a coolant, with the assembly having a handle portion spaced from the cup, such that a user can dip the receptacle and chuck in coolant while maintaining the proper orientation of the chuck in the receptacle.
According to another aspect of the invention, a kit is disclosed including a chuck and a mating receptacle for conveniently embedding a tissue sample in O.C.T. for frozen tissue sectioning.